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  • 1
    Electronic Resource
    Electronic Resource
    Intergenic and interallelic exclusion inParamecium primaurelia: Immunological comparisons between allelic and non-allelic surface antigens (1979)
    Springer
    Immunogenetics 9 (1979), S. 77-95 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract InParamecium, the expression of surface antigens is regulated in such a way that only one is generally present at the cell surface under given environmental conditions. Previous analyses have indicated that the surface antigen molecules play a key role in the control of their own expression. In order to characterize the structural particularities displayed by both allelic and non-allelic surface antigen molecules, immunological; comparisons were performed in vivo and in immunodiffusion on nine G and six D allelic surface antigens inParamecium primaurelia. Our results show: (1) it is possible to distinguish two regions in the surface antigen molecule; one accessible to antibodies in vivo, carrying specific immobilization determinants, the other not accessible to antibodies in vivo, carrying common determinants shared by all the antigens of the same allelic series. Antigens coded by different loci differ in both regions. (2) The specificity of immobilization determinants is not borne by a hypothetical carbohydrate component of the molecule but by the polypeptide chain itself. (3) In heterozygotes displaying allelic exclusion the parental surface antigen phenotypically excluded in vivo at the cell surface is not present in the cytoplasm. These data permit some interpretations concerning the mechanisms of intergenic and interallelic exclusion, on the basis of the structural differences between the different surface antigens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01570395
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  • 2
    Electronic Resource
    Electronic Resource
    Allelic modulation in Paramecium aurelia heterozygotes (1971)
    Springer
    Molecular genetics and genomics 112 (1971), S. 306-316 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The systematic study of heterozygotes for the g locus controlling G serotype in Paramecium aurelia syngen 1, shows that a phenomenon of allelic exclusion exists. This phenomenon of exclusion happens either systematically, almost systematically or randomly, depending on the studied combination of alleles (Table 2). For a given combination of alleles, it is always the same allele which is “excluded”. Back-cross experiments indicate that the observed allelic modulation is not dependent upon a simple or classical type of regulatory system. It seems to be characteristic of a given allelic interaction. This phenomenon of allelic exclusion resembles the well-known phenomenon of mutual exclusion occurring between different loci which govern the surface antigens corresponding to the different serotypes of Paramecium aurelia. Both cases of exclusion (inter-allelic or intergenic) might involve an original mechanism of inter-regulation between proteins belonging to the same molecular “family” and fulfilling similar functions but under different physiological conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334432
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  • 3
    Electronic Resource
    Electronic Resource
    Regulation of surface antigens expression in Paramecium primaurelia (1978)
    Springer
    Molecular genetics and genomics 161 (1978), S. 23-29 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Paramecium aurelia, allelic exclusion can be considered as a basic feature of the surface antigens system in the same way as intergenic exclusion. Our studies on allelic exclusion in G156/G168 heterozygotes show that (1) allelic exclusion does not depend on discrete regulatory genes dispersed throughout the genome; (2) it does not seem to be influenced by cytoplasmic factors; (3) it occurs regardless of the surface antigen expressed by the parental strains at the time of the cross. These results are discussed in relation to both intergenic and interallelic exclusion for which a common basis is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266611
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  • 4
    Electronic Resource
    Electronic Resource
    Regulation of surface antigen expression in Paramecium primaurelia. II. Role of the surface antigen itself (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 99 (1979), S. 383-393 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the wild-type strains, 156 and 168, of Paramecium primaurelia, the alleles G156 and G168 expressed at medium temperature specify two immunologically distinguishable surface antigens 156G and 168G, whose phenotypic expression shows allelic exclusion, the majority of heterozygotes being phenotypically [156G] while a small minority is phenotypically [156G-168G]. At high temperature, the antigens coded by another locus, generally the D locus, are expressed. This system, displaying both intergenic and interallelic exclusion, provides favourable material to analyze the respective roles of the genome, of the antigens expressed and of the environmental conditions, in particular temperature, on the regulation of the expression of surface antigens.This analysis was carried out by studying the variations of the expression of surface antigens as a function of temperature, culture medium and previously expressed antigens in different genetic situations (a) in homozygotes: the wild-type strains 156 and 168, and the isogenized strains “G156 isogenic 168” carrying the G156 allele in a 168 genetic background; (b) in heterozygotes of the two phenotypic classes of heterozygotes, [156G] and [156G-168G]. The results show that (1) the thermal stability of the expression of a given surface antigen and its rate of re-appearance at the cell surface depend on its own specificity: (2) in heterozygotes [156G-168G], the stability of the expression of the antigen 156G is modified and “adjusted” to that of the less stable surface antigen 168G, and (3) the surface antigen itself exerts a positive control on the maintenance of its own expression.An interpretative model of “transmembranous control” is proposed to account for the regulation of the expression of surface antigens in Paramecium.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040990313
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